A device and a method for frothing a liquid such as milk having the particulars as mentioned in the foregoing are known. For example, US 2005/0233043 discloses a device and a method for producing milk foam, wherein a pump is used for suctioning milk from a container and conveying the milk to an outlet of the device. The milk is routed through a continuous-flow heater during suctioning and heated. Furthermore, air can be added to the milk for frothing the milk.
On the basis of the application a continuous-flow heater in the known device, it is possible to use one and the same device for producing cold or hot milk foam. In particular, the continuous-flow heater is only put to an activated condition when hot milk foam needs to be produced, whereas the continuous-flow heater is kept in a deactivated condition when cold milk foam needs to be produced.
A disadvantage of applying a heater which is adapted to transfer heat to milk froth on the basis of conduction, like a continuous-flow heater, is the necessity for cleaning a surface of the heater which serves for contacting the milk froth. The same disadvantage is encountered when applying a mechanical pump for producing milk froth, as it is necessary to clean the inside of the pump after use.